I want to implement google play games services for my android game, but it seems to be missing a friends feature where you can invite/add/find friends or am i wrong? If true, then i am very surprised that its missing such an important feature.

Hi! I'm not sure this is fit for a question for the site, I feel like it's borderline opinion-based. I've been working on my game-framework for a while and I'm thinking about creating different types for the different coordinate-systems. For example the screen-coordinates and world-coordinates would be separate types, requiring explicit conversion. (This way errors such as passing in mouse-position can be avoided at type level). This came after the suggestion to represent vectors and points in space separately (https://computergraphics.stackexchange.com/questions/4290/what-is-the-difference…

I think the hard bit is determining where to cut this off. Should there also be object-local-offset that are always relative to the world position of an object? Is worldCoordA - worldCoordB always an object local offset? Do you have separate types for offsets vs coordinates in every space?

How about providing a few, provide a generic coordinate structure that the user can wrap into his own coordinate-system? And everywhere in the framework I just expect any generic one and convert into a concrete repr.

Framework should probably accept specific ones where appropriate and maybe accept any when can... I don't know Rust myself, but one part where I feel like issues might arise is when something could be of multiple types. Like a physics system comes to mind, where a body can be either added directly to the scene (world position) or where a body could be added as a child of another body (world vector/direction)